Filter cartridge and a method for its manufacture

ABSTRACT

A filter cartridge has a filter medium, which, on the circumferential side, is surrounded with clearance by a gasket-seal. A frame is arranged in the gap formed by the clearance, and is sealingly bonded to the edges of the filter medium and the gasket-seal.

BACKGROUND OF THE INVENTION

The invention relates to a filter cartridge and a method for itsmanufacture.

A filter cartridge is described in German Patent 43 23 522 A1. ThisGerman patent describes a filter cartridge that is made of azigzag-shaped, pleated filter sheeting material, arranged in a plateshape, the filter sheeting material being disposed sealingly in a frame.The frame is constituted by a U-shaped strip made of synthetic non-wovenfabric, which surrounds the pleated filter sheeting material along itslongitudinal and transverse edges and is heat-sealed to it.

SUMMARY OF THE INVENTION

An object of this invention is a filter cartridge that is simple andcost-effective to manufacture and which has a durable and tight bondbetween the filter medium, the frame, and a seal running around theframe.

The filter cartridge includes a filter medium that is circumferentiallysurrounded along its periphery by a gasket seal offset from the filterwith a clearance. A frame is arranged within the gap formed by theclearance. The frame is sealingly bonded to the filter medium edges andthe gasket-seal edges, which face each other. The entire filtercartridge constitutes one unit, which can be pre-assembled, and isparticularly simple to manufacture. The filter medium and thegasket-seal are inserted into the parting plane of a die and, to producethe frame, the edges, facing each other, are injection-molded all aroundwith the frame material during the injection-molding process in the gap.As the frame material hardens, an indissoluble claw-type fixation of theframe to the edges automatically forms. According to the presentinvention, the bond between the filter medium, the frame, and thegasket-seal is achieved in only one operation. As the material of whichthe frame is made cools and solidifies, it at least partially penetratesand sealingly accommodates itself into the facing edges of the filtermedium and gasket-seal.

The filter medium preferably is designed as an accordion fold pack. Theuse of a pleated accordion filter pack advantageously provides that thearea of the filter surface is larger than the projected surface definedby the periphery of the filter medium.

The gasket-seal is manufactured separately from the filter medium, andpreferably is designed to be ring-shaped i.e., closed upon itself. Byavoiding a joint in the gasket-seal, the danger of leaks is reduced to aminimum. In addition, errors in assembly are largely prevented.Therefore, the insertion of the closed ring gasket-seal into the partingplane of the die is straight-forward.

The filter medium and the gasket-seal are preferably each made ofnon-woven fabric. The materials of the filter medium and the gasket-sealare selected so that they bond particularly well to the injectedmaterial of the frame. In the preferred embodiment, the entire filtercartridge is made up of a total of only two different materials,assuming that the filter medium and the gasket-seal are made of anidentical non-woven fabric. This simple structure simplifies thedisposal and/or reuse of filter cartridges that have lost theirefficacy.

The frame preferably is made of a polymer material, the edges of boththe filter medium and the seal being sealingly surrounded by the frame.As a result of the indissoluble, form-locking bond of the filter mediumand gasket-seal edges to the frame, the filter cartridge of the presentinvention has very good working properties even under extremeconditions, for example, in very high or low temperatures. Thisstructural approach helps prevent any undesirable detaching of the framefrom the filter medium and/or from the gasket-seal.

BRIEF DESCRIPTION OF THE DRAWINGS

The filter cartridge according to the present invention, as well as themethod for manufacturing it, are explained in greater detail below byreference to FIGS. 1 and 2.

FIG. 1 is a perspective view of an embodiment of a filter cartridgeconstructed according to the principles of the invention; and

FIG. 2 illustrates the junction of the filter medium, the gasket seal,and the die used to form the frame.

DETAILED DESCRIPTION

An exemplary embodiment of a filter cartridge constructed according tothe principles of the present invention is shown in FIGS. 1 and 2. Toattain as large a filter surface area as possible, the filter medium 1is designed as a pleated accordion fold pack 7. In use, it is arrangedin a housing (not depicted here). Gasket-seal 2, which completelysurrounds frame 4 along its outer periphery and can be sealinglyinstalled in a housing under elastic prestressing, is designed to bering-shaped, i.e. continuous. By avoiding joints, the danger of leaks isconsiderably reduced.

In contrast to filter medium 1 and gasket-seal 2, which in thisexemplary embodiment are made of an identical non-woven fabric, frame 4is made of a polymer material, which sealingly surrounds edges 5 and 6of the filter medium 1 and the gasket-seal 2.

The manufacture of the filter cartridge is further illustrated in FIG.2. Here, the filter medium 1 (here having the form of a pleatedaccordion fold pack) and gasket-seal 2 are inserted into the partingplane 8 of a die 9. After die 9 is closed, a liquefied polymer materialis injected into gap 3, which is formed by the clearance between filtermedium 1 and gasket-seal 2. Edges 5 and 6, facing each other, of filtermedium 1 and gasket-seal 2 extend, in each case, into gap 3 and aresealingly enclosed by the still liquid, polymer material of frame 4. Asthe polymer material of frame 4 hardens, the hardening polymer materialautomatically bonds to the non-woven fabrics, forming an indissolublesealing bond between frame 4 and edges 5 and 6.

Although the gasket-seal 2 shown in FIG. 2 is cone-shaped in crosssection, it can have other shapes as well.

The dotted lines in FIG. 2 depict the boundary of edges 5 and 6 offilter medium 1 and gasket-seal 2, which are completely enclosed by thepolymer material of frame 4.

This filter cartridge is particularly useful as an automobile passengercompartment filter for filtering the air entering the automobilepassenger compartment coming from the ambient environment.

What is claimed is:
 1. A filter cartridge, comprising:a filter mediumhaving a circumferential perimeter defining edges; a gasket seal havingan edge, the gasket seal circumferentially surrounding the filter mediumso that the edges of the gasket seal and the edges of the filter mediumface each other; a gap defining a clearance between the gasket seal andthe filter medium; a frame located in the gap formed by the clearance,the frame being sealingly bonded to the facing edges of the filtermedium and the gasket-seal and having a thickness that is greater thanthe clearance defined by the gap between the gasket seal and the filtermedium.
 2. The filter cartridge as defined by claim 1, wherein thefilter medium is an accordion fold pack.
 3. The filter cartridge asdefined by claim 1, wherein the gasket-seal is separate form the filtermedium and has a closed, continuous ring shape.
 4. The filter cartridgeas defined by claim 1, wherein the filter medium and the gasket-seal aremade of a non-woven fabric.
 5. The filter cartridge as defined by claim2, wherein the filter medium and the gasket-seal are made of a non-wovenfabric.
 6. The filter cartridge as defined by claim 1, wherein the frameis made of a polymer material and the edges of the gasket seal and thefilter medium are sealingly enclosed by the frame.
 7. The filtercartridge as defined by claim 5, wherein the frame is made of a polymermaterial and the edges of the gasket seal and the filter medium aresealingly enclosed by the frame.